In recent years, the ink-jet recording system is increased in speed and size, and commercial printing utilizing the ink-jet recording system (hereinafter, referred to as “ink-jet printing”) has been started. An industrial printing machine using the ink-jet recording system for use in the commercial printing (hereinafter, referred to as “ink-jet printing machine”) has already been developed (see, for example, patent document 1). In the field of commercial printing, the number of copies printed is large, and, in view of a balance between the productivity and the printing cost, the printing speed is very important, and an ink-jet printing machine having a printing speed of 15 m/minute or more, or having a higher printing speed of 60 in/minute or more, has been developed. Further, an ink-jet printing machine of a rotary press system having mounted a pigment ink, having a further higher printing speed of more than 120 m/minute, has been developed.
The ink-jet printing machine can deal with variable information, and therefore is applied particularly to on-demand printing. In the commercial printing, a preferred mode is such that printing for fixed information is made using an offset printing machine and printing for variable information is made using an ink jet printing machine.
As an ink-jet recording paper having appearance as excellent as that of a coated paper for use in offset printing and having printability to an ink jet printer, an ink-jet recording paper having a coating layer comprised mainly of an inorganic pigment and a binder formed on at least one side of a substrate is disclosed, wherein, relative to 100 parts by mass of the total of the inorganic contents of the coating layer, more than 95 parts by mass of any one of ground calcium carbonate, precipitated calcium carbonate, and kaolin or a mixture of two or more of these pigments is contained as an inorganic content, wherein the pigment collectively has an average particle diameter in the range of from 0.02 to 2.00 μm (see, for example, patent document 2).
Ground calcium carbonate for use in an ink-jet recording sheet is disclosed, wherein the ground calcium carbonate contains ground calcium carbonate having a particle diameter of 0.1 to 1 μm in an amount of 80% by mass or more and has an average particle diameter of 0.2 to 0.4 μm (see, for example, patent document 3).